HTML5 Canvas Fire Event with Konva

To fire events with Konva, we can use the fire() method. This enables us to programmatically fire events like click, mouseover, mousemove, etc., and also fire custom events, like foo and bar.

Note: While custom events are possible, it's generally better to use built-in interaction events like click, mouseover, mousemove, etc. Custom events can make code harder to maintain and debug.

Vanilla

import Konva from 'konva';

const stage = new Konva.Stage({
  container: 'container',
  width: window.innerWidth,
  height: window.innerHeight,
});

const layer = new Konva.Layer();
stage.add(layer);

const circle = new Konva.Circle({
  x: stage.width() / 2,
  y: stage.height() / 2,
  radius: 70,
  fill: 'red',
  stroke: 'black',
  strokeWidth: 4,
});

// add shape event listener
circle.on('customEvent', function (evt) {
  alert('custom event fired');
});

// add button to trigger custom event
const button = document.createElement('button');
button.innerHTML = 'Fire Custom Event';
button.style.position = 'absolute';
button.style.top = '10px';
button.style.left = '10px';
button.style.zIndex = '1';
document.body.appendChild(button);
button.addEventListener('click', () => {
  // fire custom event
  circle.fire('customEvent', {
    bubbles: true,
  });
});

layer.add(circle);

React

import { Stage, Layer, Circle } from 'react-konva';
import { useRef } from 'react';

const App = () => {
  const circleRef = useRef();

  const handleCustomEvent = () => {
    alert('custom event fired');
  };

  const fireCustomEvent = () => {
    circleRef.current.fire('customevent', {
      bubbles: true,
    });
  };

  return (
    <>
      <button 
        onClick={fireCustomEvent}
        style={{
          position: 'absolute',
          top: '10px',
          left: '10px',
          zIndex: 1
        }}
      >
        Fire Custom Event
      </button>
      <Stage width={window.innerWidth} height={window.innerHeight}>
        <Layer>
          <Circle
            ref={circleRef}
            x={window.innerWidth / 2}
            y={window.innerHeight / 2}
            radius={70}
            fill="red"
            stroke="black"
            strokeWidth={4}
            onCustomevent={handleCustomEvent}
          />
        </Layer>
      </Stage>
    </>
  );
};

export default App;

Vue

<template>
  <div>
    <button 
      @click="fireCustomEvent"
      style="position: absolute; top: 10px; left: 10px; z-index: 1"
    >
      Fire Custom Event
    </button>
    <v-stage :config="stageSize">
      <v-layer>
        <v-circle
          ref="circleRef"
          :config="circleConfig"
          @customEvent="handleCustomEvent"
        />
      </v-layer>
    </v-stage>
  </div>
</template>

<script setup>
import { ref } from 'vue';

const circleRef = ref(null);

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const circleConfig = {
  x: window.innerWidth / 2,
  y: window.innerHeight / 2,
  radius: 70,
  fill: 'red',
  stroke: 'black',
  strokeWidth: 4
};

const handleCustomEvent = () => {
  alert('custom event fired');
};

const fireCustomEvent = () => {
  circleRef.value.getNode().fire('customevent', {
    bubbles: true,
  });
};
</script>